This invention relates to a method and apparatus that uses localized heat generation to produce a desired acoustic profile to attenuate noise propagated through an air induction system.
An internal combustion engine utilizes an air induction system to conduct air to engine cylinders. Engine noise is propagated through the air induction system, which is undesirable. Noise attenuation mechanisms have been installed within the air induction system to reduce these noises. A typical feed forward noise attenuation mechanism includes a loudspeaker, a microphone, and a signal generator/computer, which are mounted within an air inlet duct housing. The microphone detects the noise error and generates a noise error signal that is sent to the signal generator/computer. The signal generator/computer creates a corrected phase-shifted signal and sends that back to the speaker to generate a sound field that cancels out the noise that is being detected by the microphone.
While these systems can operate effectively to reduce noise, there are some disadvantages with the loudspeaker noise attenuation mechanism. One disadvantage is that a significant number of components, with associated electrical connections, are required to operate the mechanism, which increases cost and assembly time. Another disadvantage is that large speaker sizes are required to reduce engine noise levels below accepted values. Typically, engine noise must be reduced below 110 Hertz (Hz). This causes the noise attenuation mechanism to be very large, since speaker effectiveness is less at lower frequencies, taking up a considerable amount of packaging space. Additionally, these noise attenuation mechanisms draw a large amount of power from the vehicle electrical system in order to effectively cancel the high levels of low frequency noise.
Thus, it is desirable to have a method and apparatus that can reduce noise as well or better than traditional noise attenuation mechanism but operates more efficiently and effectively, with fewer components, as well as overcoming the other above mentioned deficiencies with the prior art.